1. Field of the Invention
The present invention relates to an apparatus, such as a camera, which is adapted to use a shape memory member.
2. Description of the Related Art
A proposal regarding an apparatus adapted to use a shape memory alloy as a shape memory member has been made in Japanese Patent Application No. Hei 7-19175. According to the proposal, such an apparatus includes a first cover provided with a shape memory alloy wire and a second cover provided with a solar battery, and the function of the apparatus is such that when the temperature of the shape memory alloy wire reaches a predetermined temperature, the shape memory alloy wire recovers its shape (shrinkage) and hence the engagement of a latch claw connected to the wire is released, whereby the first and second covers are made to move integrally in a direction away from the body of the apparatus by the force of a spring, thereby producing a space between the body of the apparatus and the first and second covers to prevent overheating of the body of the apparatus.
However, the construction of the above-described proposal presupposes that the shape memory alloy is used at a suppressed strain of 1% or less in the state of small hysteresis (an elasticity area) (if the hysteresis becomes large, the shape memory alloy becomes unable to recover its original shape even if a temperature fall occurs). Accordingly, the shape memory alloy can only provide a small amount of displacement with respect to a variation in the temperature of the shape memory alloy.
For this reason, in the case of a wire-shaped shape memory alloy which can be disposed within a small space in an apparatus, as shown in FIG. 12, the amount of displacement (B) of such shape memory alloy, which is obtainable from the temperature variation thereof, is extremely small the obtainable amount of displacement of a wire of approximately 80 mm long is approximately 0.3 mm, inclusive of a safety margin which ensures that the wire can always be used in the state of small hysteresis). As a result, in the case of the apparatus having the above-described construction, since the amount of engagement of a latch claw cannot be made large at normal temperatures, the first cover may open by a vibration or by a shock due to a fall.